Capacitive touch screen apparatus

ABSTRACT

A touch screen apparatus and associated methods are disclosed. In one embodiment, a touch screen apparatus includes a touch screen sensor grid including a first electrode and a second electrode. The first electrode includes a cavity in which a ground electrode is disposed. The second electrode is disposed above the ground electrode.

BACKGROUND

1. Technical Field

This disclosure relates to touch screens, and more particularly, tocapacitive touch screens.

2. Description of the Related Art

Touch screens have found widespread application in recent years. Smartphones and tablet computers are just two of a wide variety of systems inwhich touch screens are used as input devices. In general, a touchscreen is an electronic visual display through which a user can interactwith a system by touching the screen with a finger or a stylus. Touchscreens come in various types. A category of touch screens that operatebased on the changing of capacitance values when touched are referred toas capacitive touch screens.

SUMMARY OF THE DISCLOSURE

A touch screen apparatus is disclosed. In one embodiment, a touch screenapparatus includes a touch screen sensor grid including a firstelectrode and a second electrode. The first electrode includes a cavityin which a ground electrode is disposed. The second electrode isdisposed above the ground electrode.

In one embodiment, a method includes generating an electric fieldbetween a first electrode and a second electrode of a touch screenapparatus. The first electrode includes a cavity in which a groundelectrode is disposed. The second electrode disposed above the groundelectrode. The method further includes detecting a change of theelectric field responsive to a touch of the touch screen apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects of the disclosure will become apparent upon reading thefollowing detailed description and upon reference to the accompanyingdrawings, which are now described as follows.

FIG. 1 is an illustration of one embodiment of an electronic deviceincluding a touch screen.

FIGS. 2A-2D are illustrations of the various layers of one embodiment ofa touch screen apparatus.

FIG. 3 is a side view illustrating the various layers of one embodimentof a touch screen apparatus.

FIG. 4 is a schematic diagram illustrating one embodiment of anelectrical circuit formed using an embodiment of a touch screenapparatus.

FIG. 5 is a flow diagram illustrating one embodiment of a method foroperating a touch screen apparatus.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Itshould be understood, however, that the drawings and description theretoare not intended to limit the invention to the particular formdisclosed, but, on the contrary, the invention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION

Turning now to FIG. 1, an illustration of one embodiment of a portableelectronic device including a touch screen apparatus is shown. Portableelectronic device 10 in the illustrated example may be one of a numberof different types of devices, such as a smart phone, a tablet computer,or other type of device. Touch screen apparatus 25 of portableelectronic device 10 provides a user interface in the embodiment shown.The touch screen apparatus 25 may be used as a device in which usersprovide input to portable electronic device 10, as well as a device inwhich responses to user inputs and other processing actions aredisplayed. Responsive to touch by finger 15 as shown in theillustration, portable electronic device 10 may perform variousprocessing functions that may cause the information displayed to beupdated. It is noted that in some embodiments, a stylus or other type ofobject may be used to provide user input to portable electronic device10 in lieu of the finger shown in the illustration. In general, thetouch may be performed by any suitable object.

While the embodiment shown in FIG. 1 is directed to a portableelectronic device, touch screen apparatus 25 may be used in otherimplementations, which may or may not be portable. For example, anembodiment of touch screen apparatus 25 to be discussed further belowmay be implemented in a kiosk or other type of stationary display orexhibit as well as in other suitable devices.

In one embodiment, touch screen apparatus 25 may implement a capacitivetouch screen. A capacitive touch screen is one in which a touch of thetouch screen alters the capacitance between electrodes implementedtherein. The change in capacitance may in turn result in a change in anamount of current or charge received by a receiver circuit. Detection ofthe change of current or charge may indicate that the touch screen hasbeen touched. Touch screen apparatus 25 may include a number of transmitelectrodes and receive electrodes arranged across the area spanned bythe touch screen. Corresponding electric fields may be formed betweentransmit and receive electrodes where they overlap in area. Thus, when aparticular electric field is disturbed responsive to a touch of thetouch screen, circuitry coupled to the touch screen apparatus 25 maydetect the location of the touch. Responsive to detecting the touch andits location, the circuitry may perform additional processing that maycause the information displayed on the touch screen to be updated, amongother actions.

In some devices, it may be desirable to limit the thickness of touchscreens and the corresponding apparatus embodiments in which they areimplemented. In a thinner panel design, the mutual capacitance betweenthe transmit and receive electrodes may be more tightly coupled.Reducing the overlap between the transmit and receive electrodes mayhelp maintain the mutual capacitance at or near a desired value even ifthe relative geometry therebetween changes as a result of a temperaturechange. Various embodiments of such a touch screen apparatus will now bediscussed in further detail.

Turning now to FIGS. 2A-2D, a top view of a portion of variouscomponents of touch screen apparatus 25 is shown. FIG. 2A illustrates acomposite view of the electrode arrangement of touch screen apparatus25, while FIGS. 2B-2D illustrate the individual electrode types. It isnoted that the embodiments shown in FIGS. 2A-2D illustrate a portion ofthe overall area occupied by the different electrodes of touch screenapparatus 25 in various embodiments. It is further noted that the shapesof the various electrodes illustrated here are exemplary, and that suchelectrodes may be implemented using other shapes while still fallingwithin the scope of this disclosure.

In the illustrated embodiment, touch screen apparatus 25 includes anumber of transmit electrodes 252, a number of receive electrodes 258,and a number of ground electrodes 255. The area occupied by each oftransmit electrodes 252 overlaps a portion of the area occupied (inanother plane) by each of a number of receive electrodes 258. Similarly,the area occupied by each of receive electrodes 258 overlaps a portionof the area occupied by each of the transmit electrodes 252. As will beillustrated in further detail below, each of the transmit electrodes maybe coupled to a corresponding driver circuits, while each of receiveelectrodes 258 may be coupled to a corresponding receiver. When thetransmitter and receiver circuits are active, electric fields may beformed between overlapping portions of transmit electrodes 252 andreceive electrodes 258. When touch screen apparatus 25 is touched by auser, at least one of the electric fields may be disturbed due to achange in the capacitance resulting from the touch. The change in theelectric field (and more particularly, change in current or chargereceived by a corresponding receiver) may in turn provide an indicationof both the occurrence and location of the touch.

As noted above, reducing the overlapping area between transmit andreceive electrodes may reduce some of the mutual capacitancetherebetween and thus reduce the impact of unintended changes to thegeometry of the electrodes (e.g., due to temperature changes). In theembodiment shown, cavity areas 253 are slots formed in each of transmitelectrodes 252. The cavity areas 253 are formed in locations that reducethe overlapping area with receive electrodes 258 when touch screenapparatus 25 is fully assembled.

In the composite assembly shown in FIG. 2A, the transmit electrodes 252and receive electrodes 258 are arranged in proximate to one another. Thereceive electrodes 258 are located in a layer/plane arranged above(i.e., closer to the outer surface of the touch screen apparatus 25) thelayer/plane in which the transmit electrodes 252 are located.Furthermore, the transmit electrodes 252 are arranged closer to theelectronics of the system in which touch screen apparatus 25 isimplemented. Since the electronics of the device may generate noise orinterference that can affect operation of the touch screen apparatus,ground electrodes 255 are implemented to provide shielding between thedevice electronics and the receive electrodes 258. In the embodimentshown, the ground electrodes 255 are shaped such that they maysubstantially occupy the area between individual instances of thetransmit electrodes 252. Furthermore, the shape of the ground electrodesin this embodiment is such that they also occupy the cavity areas 253 ofthe transmit electrodes. In one embodiment, the ground electrodes 253may further be implemented in the same layer/plane as the transmitelectrodes 252. In another embodiment, the layer in which the groundelectrodes are implemented may overlap the layer of the transmitelectrodes, even if they are otherwise not co-planar. Accordingly,transmit electrodes 252 in combination with ground electrodes 255 mayshield receive electrodes 258 from noise generated by the electronics ofthe device in which touch screen apparatus 25 is implemented.Accordingly, the configuration shown in the illustrated embodiment mayallow for reducing the overlap between transmit electrodes 252 andreceive electrodes 258 while also providing the shielding fromelectronic noise as described above.

Turning now to FIG. 3, a side view of one embodiment of a portableelectronic device 10 including touch screen apparatus 25 is shown. Inthe embodiment shown, touch screen apparatus 25 includes a transparent(or at least partially transparent), surface 259, which may be comprisesof an electrically insulating material, and which may additionally be adielectric material. The surface 259 is arranged as the outermost layerof touch screen apparatus 25, and may thus act as the touch surfacethrough which a user may provide input to portable electronic device 10.When a user touches surface 259, either with a finger or other type ofobject (e.g., a stylus), the capacitance in the corresponding locationmay be altered, thereby altering one or more electrical fields in thatlocation.

In addition, information may be displayed through the transparent,surface 259. Although not explicitly shown here, portable electronicdevice may include one or more liquid crystal displays (LCDs), lightemitting diode (LED) displays, or other type of display apparatus thatmay emit light through surface 259. The displayed information mayinclude icons, text, and any other type of information which may begenerated by portable electronic device 10. A user may interact withportable electronic device 10 by touching the surface 259 at variouspoints. The information displayed by the device may be updatedresponsive to a user touch.

In FIG. 3, the planar relationships between transmit electrodes 252,receive electrodes 258 and ground electrodes 255 are shown for oneembodiment. In the embodiment shown, receive electrodes are arranged ina layer that is underneath that of surface 259, while being above (butin the proximity) the plane of transmit electrodes 252. In turn, thetransmit electrodes 252 are arranged in a plane that is above thedevice/sensor electronics 305 but below the plane of receive electrodes258. In the illustrated embodiment, ground electrodes 255 are arrangedto have substantially the same planar relationship with receiveelectrodes 258 as transmit electrodes 252. Thus, in accordance with bothFIG. 3 and the arrangement shown in FIGS. 2A-2D, ground electrodes 255occupy the space between individual instances of transmit electrodes252, as well as the cavity areas 253 of each transmit electrode 252.Therefore, transmit electrodes 252 and ground electrodes 255 may shieldreceive electrodes 258 from electronic noise that may be emitted bydevice/sensor electronics 305.

In the embodiment shown, each transmit electrode 252 is coupled to acorresponding driver circuit 310. Similarly, each receive electrode 258is coupled to a receiver circuit 315. One instance each of drivercircuit 310 and receiver circuit 315 are shown here for the sake ofsimplicity, although it is understood that multiple instances of eachmay be provided. Each driver circuit 310 may generate a voltage that isprovided to its correspondingly coupled transmit electrode 252. Eachreceiver circuit 315 may receive an electrical current or charge fromits correspondingly coupled receive electrode 258. As noted above, whena driver circuit 310 coupled to a transmit electrode 252 and a receivercircuit 315 coupled to an overlapping receiver circuit 315 are bothactive, an electrical field may be formed in the space between theoverlapping electrodes. This electric field may remain substantiallyconstant in strength when undisturbed. When a touch occurs to thesurface 259 in a location overlapping the area of the electric field (orclose thereto in some cases), the electric field may be altered, andthus the electrical current or charge received by receiver circuit 315may be correspondingly altered. Thus, a change to the electrical currentor charge received by a given receiver circuit 315 may be interpreted asa touch of the touch screen.

In the embodiment shown, device/sensor electronics 305 may include oneor more sensing circuits coupled to one or more of the receiver circuits315. Based on which receiver circuits 315 report a change in receivedcurrent or charge, sensing circuits within device/sensor electronics 305may determine an approximate location on the surface 259 at which thetouch occurred. Based on the touch, an appropriate response may begenerated. Exemplary responses include (but are not limited to) updatingor changing information, initiating a phone call, answering a phonecall, typing a character of a text message, sending a text message,invoking an application, and so on.

In addition to the sensing circuitry discussed above, device/sensorelectronics 305 may include various other types of circuits. Suchcircuits may include (but are not limited to) general-purposeprocessors/processor cores, graphics processors, various types of radiotransceivers, audio processing circuitry, and so on. The circuitry ofdevice/sensor electronics 305 may be implemented using one or moreintegrated circuits. In additional, some portions of device/sensorelectronics may be implemented using one or more discrete components.

FIG. 4 is a diagram illustrating the electrical circuit formedoverlapping portions of a transmit electrode and a receive electrode andtheir correspondingly coupled driver and receiver circuits,respectively. In the embodiment shown, touch screen apparatus 25 isrepresented by a variable capacitance. The capacitance between atransmit electrode 252 and an overlapping portion of a receive electrodemay be considered variable due to the change that occurs responsive to atouch in the corresponding proximity. As noted above, driver circuit 310may generate a voltage that is provided to the transmit electrode 252 ofthe overlapping portions. Receiver circuit 315 may be coupled to thereceive electrode 258 of the overlapping portions. In one embodiment,driver circuit 310 may generate an alternating current (AC) voltage.Accordingly, receiver circuit 315 may receive an AC signal via theformed capacitor. When a touch alters the capacitance of the overlappingsections of the transmit electrode 252 and the receive electrode 258,the current of the AC signal may change accordingly. This change incurrent may be detected by receiver circuit 315 and reported todevice/sensor electronics 305, which may then determine the locationupon which the touch occurred.

FIG. 5 is a flow diagram illustrating one embodiment of a method foroperating a touch screen apparatus. The methodology described herein andillustrated by FIG. 5 may be applied to the various embodiments of touchscreen apparatus 25 discussed above, among others.

Method 500 begins with the generation of electric fields betweentransmit electrodes and receive electrodes of a touch screen apparatus(block 505). The electric fields may be generated based on a capacitancebetween overlapping portions of transmit and receive electrodes of atouch screen apparatus. The electrodes may be arranged such that groundelectrodes fill in gaps between and in the transmit electrodes t shieldthe receive electrodes from electronic noise generated by other circuitsin the system in which the touch screen apparatus is implemented.

The method further includes detecting a change in at least one of theelectric fields responsive to a touch of the touch screen (block 510).The change in the electric field may result from a change in capacitancebetween transmit and receive electrodes in the proximity of the touch.The change in the electric field may be detected via a change in currentreceived by a receiver circuit coupled to a corresponding receiveelectrode. The detection of the changing current may be reported tosensor electronics in one embodiment, which may in turn determine thelocation of the touch (block 515). The system in which the touch screenapparatus is implemented may generate a system response to the touchupon its detection and determination of its location (block 520). Theresponsive may include one of a number of different actions, some ofwhich may include an update of the information displayed on the touchscreen. The method may return to block 510 and repeat blocks 510, 515,and 520 for each touch of the touch screen.

While the present invention has been described with reference toparticular embodiments, it will be understood that the embodiments areillustrative and that the invention scope is not so limited. Anyvariations, modifications, additions, and improvements to theembodiments described are possible. These variations, modifications,additions, and improvements may fall within the scope of the inventionsas detailed within the following claims.

What is claimed is:
 1. An apparatus comprising: a touch screen sensorgrid including a first electrode and a second electrode; wherein thefirst electrode has a cavity in which a ground electrode is disposed,and wherein the second electrode is disposed above the ground electrode.2. The apparatus as recited in claim 1, wherein the first electrode andthe ground electrode are arranged in a first plane and wherein thesecond electrode is arranged in a second layer.
 3. The apparatus asrecited in claim 2, further comprising a surface layer arranged abovethe second electrode, wherein the surface layer is at least partiallytransparent.
 4. The apparatus as recited in claim 1, wherein the firstelectrode is coupled to an output of a driver circuit, and wherein thesecond electrode is coupled to a receiver circuit.
 5. The apparatus asrecited in claim 4, wherein the driver circuit is configured to drive asignal onto the first electrode such that an electric field is formedbetween the first and second electrodes.
 6. The apparatus as recited inclaim 5, wherein the receiver circuitry is configured to detect a changein an electrical charge responsive to a change in the electric fieldresulting from an object touching the touch screen.
 7. The apparatus asrecited in claim 6, further comprising sensor circuitry coupled to thereceiver circuit, wherein the sensor circuitry is configured to detectan approximate location of a touch of the touch screen.
 8. The apparatusas recited in claim 1, wherein the first and second electrodes arearranged to reduce a change in a capacitance between the first andsecond electrodes resulting from a change in temperature.
 9. A methodcomprising: generating an electric field between a first electrode and asecond electrode of a touch screen apparatus, wherein the firstelectrode includes a cavity in which a ground electrode is disposed, andwherein the second electrode disposed above the ground electrode; anddetecting a change of the electric field responsive to a touch of thetouch screen apparatus.
 10. The method as recited in claim 9 furthercomprising: driving a first electrical signal from a driver circuit tothe first electrode; and receiving a second electrical signal from thesecond electrode at the receiver circuit.
 11. The method as recited in9, further comprising the ground electrode and the first electrodeshielding the second electrode from electrical noise generated by one ormore integrated circuits disposed beneath the first electrode and groundelectrode.
 12. The method as recited in claim 9, further comprisingdetermining a location at which the touch screen apparatus was touchedand updating information displayed on a display screen of the touchscreen apparatus.
 13. The method as recited in claim 12, furthercomprising reducing a change in a capacitance between the first andsecond electrodes resulting from a change in temperature.
 14. A touchscreen device comprising: a receive electrode; a transmit electrodearranged proximate to the receive electrode, wherein the transmitelectrode includes at least one slot in which a ground electrode isdisposed, and wherein the receive electrode is disposed above the groundelectrode.
 15. The touch screen device as recited in claim 14, whereinthe transmit electrode and the ground electrode are arranged in a firstplane, and wherein the receive electrode is arranged in a second plane.16. The touch screen device as recited in claim 15, further comprising asurface arranged above the second electrode, wherein the surface is atleast partially transparent.
 17. The touch screen device as recited inclaim 16, further comprising a driver circuit configured to provide avoltage to the transmit electrode, and a receiver circuit coupled toreceive an electrical charge from the receive electrode.
 18. The touchscreen device as recited in claim 17, wherein the driver circuit isconfigured to drive a signal onto the transmit electrode such that anelectric field is formed between the transmit and receive electrodes.19. The touch screen device as recited in claim 17, wherein the receivercircuit is configured to detect a change in an amount of electricalcharge received from the receive electrode responsive to an objecttouching the surface.
 20. The touch screen device as recited in claim14, wherein the transmit and receive electrodes are arranged to reduce achange in a capacitance between the transmit and receive electrodesresulting from a change in temperature.